The authors report their experiences in raising armadillos and the results obtained in inoculating them with M. leprae. They begin by reporting on the origin of the animals, how they were captured, and their efforts until they found the right kind of housing for the armadillos. They also tell of their attempts to develop the correct feeding procedures. The result is the feed used now in their laboratory: chicken feed mixed with bread, eggs, meat and milk. Along with this, they report on the way each animal is registered and the examination it undergoes upon admittance, namely, recording of its weight, rectal temperature, feces examination, hemogram and hemossedimentation. They also tell how animals are immobilized so as to take blood samples for the inoculations. Lastly, they present the results of the inoculations with M. leprae in three armadillos of the Euphractus sexticinctus species and 26 of the Dasypus novemcinctus species, with special reference to an armadillo of the D. novemcinctus species, which had systemic infection 15 months after being inoculated subcutaneously and intravenously. Bacilli were found in large quantities in various organs like the skin, lymph nodes, liver, kidneys and spleen. No bacilli were found in the myocardium, pancreas, thyroid and testicles. The authors are of the opinion that this is the first armadillo of the D. novemcinctus species to present experimental systemic infection with M. leprae in South America. Another armadillo, which has been inoculated with a suspension of 1.2 X 10(8) bacilli by the intracardiac route already showed nodules with bacilli on the abdominal wall 10 months after being inoculated. They believe that the results already obtained indicate that soon they will be able to provide material for institutions in Brazil as well as other countries that are interested in the study of M. leprae and in the preparation of the Mitsuda antigen which is so vital to the control of Hansen's disease.